1. Field of the Invention
The present invention generally related to systems and methods for photographic enhancement by blending of contrast adapted and non-contrast-adapted versions of the same image.
2. Background
Many current devices are available for capturing images. For example, current digital cameras and modern cell phones and tablets can all capture and display digital images to a user. In more cases, these devices capture images using a pre-defined dynamic range of illumination across the entire captured image. For example, these cameras may capture images at a preselected exposure level and a predefined contrast range.
In digital photography, High Dynamic Range (HDR) technology enables photographers to capture a greater range of tonal detail by capturing a greater dynamic range between the lightest and the darkest areas of a captured image. The dynamic range of the real world is large, and can usually be more than five orders of magnitude at the same time. The dynamic range of everyday scenes can hardly be recorded by a conventional sensor. Hence, a conventional image may contain portions that are over-exposed or under-exposed. HDR imaging techniques allow the possibility to reconstruct a radiance map that covers the full dynamic range by combining multiple exposures of the same scene. For example, HDR technology may be used to bring out detail in a dark foreground object set against a bright background. High Dynamic Range (HDR) technology typically consists of (1) acquiring a wide dynamic range image and (2) adapting the wide dynamic range image to fit to the display range of the device. The first part can be achieved by using a special sensor or by combining two or more images with the same or different exposures. The second part locally adapts the tone mapping function to the display range of the device, thus it effectively enables local re-use of the available range. The second part, contrast adaptation, may be done without the first part; therefore the first part is considered to be optional.
However, a captured scene is often well illuminated with the exception of some salient areas, such as a face or other important element. Adapting the whole image may be undesirable since natural backgrounds such as foliage, land, and ocean have pre-stored representations in the brain and artificially changing the contrast may change the image perception.